1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly, to a liquid crystal display panel being able to display frames without flicker.
2. Description of the Prior Art
Thin-film-transistor (TFT) liquid crystal display (LCD) panels utilize TFTs arranged in matrix together with other suitable electronic devices to drive liquid crystal pixels in the TFT LCD panels so as to generate colorful pictures. The TFT-LCD panels have been widely applied to portable information products, such as notebook and PDA, etc., due to having characteristics, such as thin thickness, low power consumption and no radiation pollution, and the TFT-LCD panels even have been gradually replaced the cathode ray tube (CRT) monitors of traditional desktop computers.
Refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram illustrating an LCD panel according to the prior art, and FIG. 2 is a schematic diagram illustrating an equivalent circuit of a pixel in the LCD panel according to the prior art. As shown in FIG. 1, the LCD panel 10 includes a first substrate 12, a second substrate 14, a liquid crystal layer (not shown in figure), a plurality of scan lines 16, a plurality of data lines 18, and a plurality of pixels 20. The scan lines 16 and the data lines 18 are disposed on the first substrate 12, and any two of the scan lines 16 and any two of the data lines 18 define a pixel 20. In addition, the LCD panel 10 further includes a plurality of gate driving ICs 22 and a plurality of data driving ICs 24, disposed on the first substrate 12. A signal-input end 26 of each scan line 16 is electrically connected to the corresponding gate driving IC 22, respectively, and the data lines 18 are electrically connected to the data driving ICs 24. As shown in FIG. 2, each pixel 20 includes a TFT 28, a coupling capacitor Cgd, a liquid crystal capacitor Clc and a storage capacitor Cs. The coupling capacitor Cgd is a parasitical capacitor in the TFT 28 formed by a gate electrode 30 and a drain electrode 32 of the TFT 28 coupled to each other. The liquid crystal capacitor Clc is composed of a pixel electrode 33, a common electrode 34 disposed on the second substrate 14, and the liquid crystal layer in each pixel 20. The storage capacitor Cs is generated by the pixel electrode 33 and a common line 36 disposed on the first substrate 12 coupled to each other. Furthermore, a source electrode 38 of the TFT 28 is electrically connected to the corresponding data line 18, and the gate electrode 32 is electrically connected to the corresponding scan line 16. The drain electrode 32 is electrically connected to the corresponding pixel electrode 33.
When the LCD panel 10 displays, the gate driving ICs 22 transfer gate signals to each scan line 16 in turn, respectively, and then, each TFT 28 is turned on through the corresponding scan line 16. Since each TFT 28 is received the gate signal, pixel signals are respectively transferred to the source electrodes 38 of the TFTs 28 from each data driving IC 24 through each data line 18, and each pixel signal is stored at each drain electrode 32 and each pixel electrode 33 in each pixel. Thereafter, the gate signals are closed, and the pixel signals remain to stay at the pixel electrode 33, so that the required frame can be displayed. In the displaying process, the voltage of the gate electrode 30 is dropped by a voltage drop, which is generated by the change from transferring the gate signal to stopping transferring the gate signal, and each gate electrode 30 is coupled to the corresponding drain electrode 32 through the coupling capacitor between the gate electrode 30 and the drain electrode 32, so that the voltage of the pixel electrode 33 will also be affected by the voltage drop of the gate electrode 30 so as to be dropped while stopping transferring the gate signal. The voltage drop of the pixel electrode 33 is called feed-through voltage, and can be calculated by a formula ΔVp=[(Cgd)/(Clc+Cs+Cgd)]×ΔVg, wherein ΔVp is a voltage drop of the pixel electrode 33, and ΔVg is a voltage drop of the gate electrode 30.
Furthermore, each scan line can be regarded as a plurality of resistors in series, and the coupling capacitor, the liquid crystal capacitor and the storage capacitor will be combined with the resistors so as to generate the RC effect, so that the gate signal is affected by the RC effect during being transferred from the signal-input end to the terminal end. The shape of the signal wave is changed from square to rounded shape so as to have a problem of insufficient voltage being charged to the pixel electrode closer to the terminal end of the scan line. In addition, the voltage drop ΔVg of the gate electrode is affected by the RC effect, so that the pixels in a same scan line also have different voltage drops according to the formula of feed-through voltage. Therefore, error pixel signals are easily detected, which result in the displaying frames with insufficient brightness and flicker.